Display panel filter for connection to a display panel

ABSTRACT

The present invention provides a device in the form of a filter which is useable in conjunction with a plasma display panel, which is applied to the front face of a display, and which functions to reduce reflection after assembly to acceptable levels, to increase contrast enhancement ratios, to reduce EMI emissions to levels which comply with consumer safety regulations and with military and aircraft standards and to reduce infrared transmission in the 800 nm-1000 nm range to a level which does not interfere with IR remote control operation. The present invention also relates to a method of making such a plasma display panel filter and device.

[0001] This application claims the benefit of Provisional ApplicationSerial No. 60/116,562 filed Jan. 21, 1999.

FIELD OF THE INVENTION

[0002] The present invention relates generally to a display panelfilter, and more particularly to a filter having particular applicationfor use with a plasma display panel or flat panel display. The presentinvention also relates to an IR/EMI filter film applied to a substratefor use in a display panel filter or otherwise and a method of makingsuch a film and a display panel filter. The invention also relates toapplying the display panel filter directly to a display panel andlaminating the optical film between a pair of substrates in which one isa thin plastic film such as PET or other optical film.

DESCRIPTION OF THE PRIOR ART

[0003] Visual display panels commonly known as plasma display panels orflat panel displays have been recently introduced for the purpose ofdisplaying visual images or information on relatively large, flatscreens. Plasma display panel technology utilizes selectively energizedgas ions to bombard phosphors on a display screen, similar to anelectron beam bombarding phosphors on a cathode ray tube (CRT) screen.Plasma display panels are similar to CRT displays in that both provide ameans for visually displaying information or images from an inputsignal; however, important differences exist. First, a CRT displayrequires a significant depth dimension relative to the size of itsdisplay screen to accommodate a generally funnel shaped rearward portionfor generation and deflection of the electron beam. Second, most CRTscreens are curved. In contrast, the energization of the ions in adisplay panel using plasma display technology occurs in a relativelythin vacuum chamber adjacent to the display screen, resulting in arelatively thin display panel with a flat view face. Thus, plasmadisplay panels are currently used primarily for relatively large displaypanels where CRTs are impractical or where a display panel with asignificantly reduced depth dimension is necessary or desirable.

[0004] Although plasma display panels provide significant advantages andimprovements by facilitating relatively large visual displays with areduced panel depth and by otherwise facilitating the use of displays inenvironments with space restrictions which preclude the use ofconventional CRT displays, new problems have arisen. These problemsrelate to the quality of the visual display, increased infrared (IR) andelectromagnetic interference (EMI) emissions, low contrast ratio andconsumer safety issues. For example, photopic reflection from manyplasma display panels is in excess of 15%. This adversely affects thequality of the display. Further, operation of the plasma display panelproduces or has the potential of producing infrared (IR) emissions whichare capable in some cases of interfering with a remote control of thepanel or other devices utilizing infrared signaling. Still further,operation of the plasma display panel results in the generation andemission of electromagnetic interference (EMI). Accordingly, many plasmapanel displays fail to meet governmental TCO and FCC requirements forEMI emissions and the stricter standards for various military, aircraftand other uses. The above problems necessary limit the applicability anddesirability of using plasma display panels.

[0005] Accordingly, there is a critical need in the art for a device ora filter, and in particular a multi-layer filter film, useable inconjunction with plasma display panels for addressing and solving theabove problems and limitations. A need also exists for a method ofmaking such a device, filter or film.

SUMMARY OF THE INVENTION

[0006] To satisfy the need in the art, the present invention provides adevice in the form of a single filter which is useable in conjunctionwith plasma display panels or other applications and which functions toreduce reflection after assembly to acceptable levels, to increasecontrast enhancement, to maintain transmission integrity, to assist inreducing EMI emissions to levels which comply not only with consumersafety regulations, but preferably with various stricter standards, andto reduce infrared emissions in the 800 nm-1000 nm range to a levelwhich does not interfere with remote control operation.

[0007] Generally, the present invention comprises a substrate with afilter film (preferably an optical IR/EMI shielding film) appliedthereto for use in a display panel filter. One embodiment of a filterdevice in accordance with the invention includes a filter film comprisedof one or more conductive layers and one or more dielectric layersapplied to a substrate which is then laminated to a second substrate.This second substrate may comprise a piece of transparent glass, plasticor other material, a thin flexible film such as PET or other opticallyclear film or the front face of the display device itself. Thecombination of the conductive and dielectric layers functions to providethe desired EMI and IR shielding and assists in reducing reflection andincreasing contrast enhancement. This combination of layers may beprovided as a single film containing both conductive and dielectriclayers. Because lamination of the substrates necessarily requires use ofan adhesive or other bonding agent and exposure of the same to at leastone surface of the shielding film or filter, a layer of silicon dioxide(SiO₂) or other material may be applied to the filter or film, ifdesired, to improve compatibility with and/or limit possible reactionsbetween the outer layer of the filter or film and the adhesive. Theouter surfaces of one or both substrates is also preferably ananti-reflective (AR) coating. The filter further includes an electricalconnection member electrically connected to conductive layers within theEMI/IR shielding film. Grounding means is also provided in the form ofan electrical wire or the like for electrically connecting theelectrical connection member to a grounded terminal. Other means,however, may also be utilized.

[0008] The preferred embodiment of the shielding film comprises one ormore layers of a conductive material and one or more alternating layersof a dielectric. The conductive material may include various conductivemetals or other materials such as silver, copper, gold and indium tinoxide, among others, although silver metal is preferred. The dielectricmay include various materials such as niobium pentoxide, titaniumdioxide and tin oxide, among others, although niobium pentoxide ispreferred. Additionally, a thin protective layer is provided betweenadjacent conductive/dielectric layers to eliminate or limit undesirableoxidation or other deterioration of the conductive layer duringformation of the film or otherwise. Such a protective layer is desirablewhen the conductive layer is subject to oxidation or other deteriorationand/or the manufacturing conditions result in the film being exposed tohigh temperatures. Such conditions exist when the film is manufacturedusing sputtering or various other thin film deposition techniques,particularly for multiple layer films of two or more conductive materiallayers. In some cases, the protective layer is comprised of two or morelayers of different materials.

[0009] In the preferred embodiment, the transparent substrates compriseview side and panel side substrates with the panel side substrate beingthe substrate closest to, or adjacent to, the display screen. Similarly,each of the substrates includes a view side facing away from the displayscreen and a panel side facing the display screen. In one embodiment,the EMI/IR shielding film or filter is applied directly to one side ofone of the substrates and is then laminated to a second substrate by aurethane or other adhesive with the optical shielding film positionedtherebetween. The laminated substrates are then mounted in front of adisplay with the first substrate preferably adjacent to the display.This embodiment further includes an environmental degradation barrierfor the conductive layers within the EMI/IR shielding layer. Thisbarrier extends around the edge of the laminated filter and isconstructed of a conductive material. This barrier is electricallyconnected both with the electrical connection member or busbar and witha grounding terminal.

[0010] In a further embodiment, the EMI/IR shielding film or filter isapplied to the panel side of the view side substrate (the substratefurthest from the display). Subsequently, such substrate, with the filmapplied thereto, is laminated onto, or otherwise applied directly to,the front face of the display with the optical film positionedtherebetween.

[0011] In a still further embodiment, the optical film is applied to afirst substrate, with a second substrate in the form of a thintransparent plastic film such as, but not limited to,polyethyleneterephthalate (PET) laminated to the first substrate with athickness preferably less than about 0.06 inches (60 mils).Subsequently, the laminated structure is applied directly to, or mountedin front of, the front face of a display unit.

[0012] One aspect of the method of the present invention relates to amethod of making a film or filter of the type described above for use inconjunction with a plasma display panel. Such method generally includesproviding a transparent substrate, applying an EMI/IR shielding film orfilter to such substrate and then laminating such substrate to a secondsubstrate. A further aspect of the method is to apply such substrate,with the film thereon, directly to the front face of the flat panel orother display. A still further aspect of the method is to laminate acoated substrate to a second substrate comprised of a plastic film suchas PET and then applying it to, or mounting it in front of, a displayunit.

[0013] Accordingly, an object of present invention is to provide a filmor filter for use in conjunction with a plasma display panel.

[0014] Another object of the present invention is to provide a plasmadisplay panel filter which provides anti-reflective, EMI shielding,contrast enhancement and infrared shielding capabilities and which alsocomplies with consumer safety requirements.

[0015] A further object of the present invention is to provide a plasmadisplay panel filter having one or more conductive layers and one ormore dielectric layers formed on a transparent substrate for subsequentlamination to a second substrate.

[0016] A still further object of the present invention is to provide aplasma display panel filter with an improved film providing both EMI andIR shielding capabilities.

[0017] A further object of the present invention is to provide a plasmadisplay panel filter with an improved means for electrically connectingthe EMI shielding layer to a grounding terminal.

[0018] A still further object of the present invention is to provide aplasma display panel fiter with an electrically conductive materialaround the edge of the filter to prevent environmental degradation ofthe EMI shielding layer and to maximize the EMI shielding efficiency ofsuch layer.

[0019] A still further object of the present invention is to provide aplasma display panel as described above which includes a layer toprevent or minimize possible reactions between the lamination adhesiveand the shielding film and/or to improve compatibility with the adhesiveand promote the adhesive strength.

[0020] Another object of the present invention is to provide a substratewith an optical EMI/IR shielding film thereon which is applied directlyto the front face of a display or display panel.

[0021] A still further object of the present invention is to provide anoptical filter comprised of an optical film laminated between a firstsubstrate and a second substrate comprised of a plastic film such asPET.

[0022] Another object of the present invention is to provide a method ofmaking a film and plasma display panel filter of the type describedabove.

[0023] A still further object of the present invention is a method ofmaking a substrate with an EMI/IR shielding film as described above andapplying the same directly to the front face of a display.

[0024] These and other objects of the present invention will becomeapparent with reference to the drawings, the description of thepreferred embodiment and method and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is an isometric, exploded view of a plasma display paneland associated filter in accordance with the present invention.

[0026]FIG. 2 is an enlarged view, partially in section, of oneembodiment of a plasma display panel filter as viewed along the sectionline 2-2 of FIG. 1.

[0027]FIG. 3 is a schematic sectional view of the EMI/IR shielding filmin accordance with the present invention.

[0028]FIG. 4 is a view similar to that of FIG. 2 of a further plasmadisplay panel filter.

[0029]FIG. 5 is an enlarged view, partially in section, and similar tothat of FIG. 2, of a further embodiment of a plasma display panelfilter.

[0030]FIG. 6 is a schematic sectional view of a further embodiment ofthe shielding film in accordance with the present invention.

[0031]FIG. 7 is a view showing application of a coated substratedirectly to the front face of a display.

[0032]FIG. 8 is a view showing lamination of a coated substrate to asecond substrate comprised of a plastic film.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND METHOD

[0033] The present invention relates to a plasma display panel filter,or shielding film for use therein, which functions to provide EMI and IRshielding capabilities. Preferably the filter also providesanti-reflective (AR) capability. Various features of the presentinvention have possible application other than for display panelfilters. However, the description of the preferred embodiment will befor use in a plasma display panel filter.

[0034] Reference is first made to FIG. 1 illustrating an exploded,isometric view of a plasma display panel 10 and associated filter 14 inaccordance with the present invention. The display panel 10 asillustrated in FIG. 1 in accordance with the preferred embodiment is agenerally rectangular configured device having a front viewing ordisplay screen 11 and a recessed area 12 for receiving a display panelfilter 14. It should be understood, however, that the possiblerelationships between a plasma display panel and a filter in accordancewith the present invention is not limited to the embodiment disclosed inFIG. 1. If desired, the display panel 10 can be assembled with thefilter 14 being an integral part of the panel 10. Alternatively, thepanel 10 and filter 14 can be separate, stand alone items which arepurchased separately. In such case, means may be provided for suspendingthe filter 14 from a portion of the panel 10 or connecting the filter 14to the panel 10 so that the filter 14 is directly in front of andsubstantially adjacent to the display screen 11. It is also contemplatedthat the filter can be bonded or laminated directly to the displayscreen 11, if desired.

[0035] With continuing reference to FIG. 1, the filter 14 of thepreferred embodiment includes a generally flat, planer filter lamination15 having a view side 16 facing away from the display screen 11 and anopposite panel side 17 facing the display screen 11. The filter 14further includes an electrically conductive element 18 in the form of astrip of conductive material applied to the peripheral edge of thefilter lamination 15. As illustrated in FIG. 1, the electricallyconductive material 18 of the preferred embodiment extends around theperiphery of the lamination 15 and for a limited distance inwardly onboth the view side 16 and the panel side 17. As will be described ingreater detail below, the conductive element 18 functions in conjunctionwith electrically conductive layers within the lamination 15 to provideEMI and other shielding capability to the filter. Grounding meanscomprised of one or more grounding clips 19 with an electrical lead 20,or some other means, is commonly electrically connected with theconductor 18 for electrically connecting the conductor 18 to a groundterminal 21.

[0036] Reference is next made to FIG. 2 which is a partial sectionalview of the filter lamination 15 as viewed along the section line 2-2 ofFIG. 1. In general, the filter lamination 15 includes a pair oftransparent substrates 22 and 24. In the preferred embodiment, thesubstrate 22 is the view side substrate and the substrate 24 is thepanel side substrate. Each of the substrates 22 and 24 is provided withan anti-reflective coating 25 and 26, respectfully, which is applied tothe outer surfaces of the substrates, namely, to the view side of theview side panel and the panel side of the panel side panel. An EMI/IRshielding film 27 comprised of a combination of dielectric andconductive layers is applied to the view side of the panel sidesubstrate 24 and between the substrate 22 and 24 to reduce and limit EMIemissions and to provide infrared shielding and contrast enhancement.The film 27 is thus laminated between the substrates 22 and 24 via theadhesive or lamination layer 30 after being applied to the substrate 24by sputtering.

[0037] In the preferred embodiment, the transparent substrates 22 and 24are comprised of generally flat, planer sheets of glass. It iscontemplated, however, that the transparent substrates 22 and 24 could,if desired, be constructed of a transparent plastic or other syntheticmaterial or a composite glass/synthetic material. The thicknesses of thesubstrates 22 and 24 should be selected to be as thin as possible whilestill being thick enough to provide the necessary and desirable safetyand strength characteristics. In the preferred embodiment, the thicknessof the substrates is preferably in the range of about 1.0 mm to about6.0 mm or less for a filter having a viewing surface of about 2-10square feet. However, it is contemplated that at least one of thesubstrates 22, 24 could also be a thin film synthetic material such aspolyethylene terapthalate (PET) on the order of 0.010 inches thick,however, other film thickness would work as well. One of the substratescould also be the front face of a display device if the one substratewith film thereon is laminated directly to the display device.

[0038] The anti-reflective coating 25 applied to the view side of thesubstrate 22, is similar to the anti-reflective coating 26 applied tothe panel side of the substrate 24, and can be any anti-reflectivecoating known in the art. Preferably, the anti-reflective coatings 25and 26 in accordance with the present invention are comprised of aplurality of individual layers which are applied to the respectivesurfaces of the substrates 22 and 24 via sputtering or reactivesputtering in accordance with processes known in the art. The particularmakeup of these anti-reflective coatings should be effective to reducethe photopic reflection from the view side 16 and panel side 17 of thefilter 15 to an acceptable level. In a structure incorporating thefilter of the present invention, the photopic reflection normallyexhibited by the display screen 11 (FIG. 1) is significantly reduced insome embodiments by as much as a factor of 10 or more, from a reflectionof over 15% to a reflection of about 4 or 5% to 1.0% or less.

[0039] The specific structure of the anti-reflective coatings 25 and 26is described in U.S. Pat. No. 5,372,874, the substance of which isincorporated herein by reference, and is currently sold by Viratec ThinFilms, Inc. of Faribault, Minn. under the trademark CDAR. Otheranti-reflective coatings, however, can also be used.

[0040] The film 27 is comprised of a combination of dielectric andconductive layers and is primarily designed to reduce the EMI and IRemissions to acceptable levels, while at the same time minimizing anyadverse affect on the transmission of visible light through the filter.The film 27 is transparent and each of its dielectric and conductivelayers is transparent. In the preferred embodiment, the film 27 isapplied to the view side of the panel substrate 24 by sputtering orreactive sputtering and comprises a series of dielectric layersseparated by layers of an electrically conductive material.Specifically, the film 27 includes four dielectric layers 50, 54, 58 and61 and three interleaved electrically conductive layers 51, 55 and 59.

[0041] With reference to FIG. 3, the layers 50, 54, 58 and 61 are layersof relatively high refractive index dielectrics having a refractiveindex of at least 1.7 and preferably about 2.2 to 2.8. The layers 51, 55and 59 are layers of electrically conductive materials such asconductive metals. In some film 27 structures, layers 52, 56 and 60 of afurther metal or other material are added adjacent to the conductivelayers 51, 55 and 59 to prevent oxidation of the conductive layersduring deposition of the dielectric layers 54, 58 and 61.

[0042] The electrically conductive layers 51, 55 and 59 functionprimarily to reduce IR and EMI emissions generated in the plasma displaypanel. Preferably, EMI emissions are reduced to levels which comply withvarious governmental or other regulations or standards. In general, thethicker the conductive layers 51, 55 and 59, the more effective they arein reducing IR and EMI emissions. However, increasing the thickness ofthe conductive layers 51, 55 and 59 also lowers the transmission ofvisible light. Thus, to obtain the desired shielding capability, two ormore, and preferably three, conductive layers of limited thickness arepreferred. In the preferred embodiment, the conductive material layers51, 55 and 59 are silver; however, various other conductive materialscan be used as well including materials such as copper, gold and indiumtin oxide, among others. Preferably, each of the layers 51, 55 and 59has a thickness of about 5 mn to 20 nm and more preferably a thicknessof about 10 nm to 15 nm. Most preferably, the thicknesses of the layers51, 55 and 59 are 12 nm, 13 nm and 12 nm, respectively. The conductivelayers are preferably applied by sputtering, reactive sputtering, orother thin film deposition techniques.

[0043] The dielectric layers 50, 54, 58 and 61 are high refractive indexmaterials and function primarily to reduce reflectivity, and thusimprove transmission of visible light in the regions of about 380 nm to800 nm. In the preferred embodiment, the dielectric material of thelayers 50, 54, 58 and 61 may include materials such as niobium pentoxide(Nb₂O₅), titanium dioxide (TiO₂) and tin oxide (SnO₂), among others.Preferably, however, the dielectric material is niobium pentoxide(Nb₂O₅).

[0044] The outer dielectric layers 50 and 61 have a preferred opticalthickness of between about 0.4 to 0.8 at a wavelength of about 450 nm to650 nm, while the inner dielectric layers 54 and 58 have an opticalthickness between about 0.7 to 1.5 at a wavelength of about 450 nm to650 nm. As used above and throughout this application, the term “opticalthickness” shall mean the “quarter wave optical thickness” or QWOT as itis known in the art. Preferably, the physical thickness of the outerlayers 50 and 61 is about 20 nm to 50 nm and most preferably is about 30nm to 40 nm. The physical thickness of the inner dielectric layers 54and 58 is preferably about 50 nm to 90 nm and is most preferably about60 nm to 70 nm.

[0045] In some structures where the film 27 is formed by sputtering orreactive sputtering, the various film layers and the conductive materialis reactive to one or more of the materials making up the adjacentlayer. In such cases, it is necessary to first provide a thin protectiveor sacrificial material layer next to the conductive material layer toprevent its oxidation or other reaction to the reactive materials of thedielectric layers. In the embodiment of FIG. 3, the layers 52, 56 and 60perform such a function. In the preferred structure of FIG. 3, a thinlayer of titanium or some other sacrificial material is applied adjacentto the conductive material layer so that when the Nb₂O₅ or otherdielectric material is applied by sputtering or reactive sputtering, theoxygen oxidizes the titanium layer 52, 56 and 60 to TiO₂ rather than theconductive layer 51, 55 and 59. The oxidized titanium layer then formspart of the adjacent dielectric layer. In the preferred embodiment, thethickness of the protective layers 52, 56 and 60 are about 0.5 nm to 5nm and most preferably about 3 nm to 5 nm.

[0046] The preferred embodiment of the film 27 is a seven layer filmcomprising three conductive material layers and four dielectric materiallayers. It is contemplated, however, that films with different totallayers can also be utilized. Preferably, however, the number ofdielectric layers should exceed the number of conductive layers by one.Thus, where n equals the number of conductive layers, the number ofdielectric layers is preferably n+1.

[0047] Accordingly, the film 27 of FIG. 2 comprises a plurality ofconductive and dielectric layers including a pair of end dielectriclayers and alternating conductive and inner dielectric layers disposedtherebetween. The end dielectric layers have an optical thickness ofbetween about 0.4 to 0.8 and preferably 0.6 at a wavelength of about 450nm to 650 nm, the inner dielectric layers have an optical thickness ofabout 0.7 to 1.5 at a wavelength of about 450 nm to 650 nm and theconductive layers have a physical thickness of about 5 nm to 15 nm.

[0048] In the embodiment of FIG. 2, the film 27 is applied by sputteringthe various film layers to the view side of the panel side or filmcarrying substrate 24, with the layer 50 sputtered first and thenfollowed by the layer 51, the layer 52 and sequentially by the layers54, 55, 56, 58, 59, 60 and 61. The film carrying substrate 24 is thenlaminated to the substrate 22 via the adhesive or lamination layer 30,with the film 27 facing the substrate 22. The lamination material 30 inthe preferred embodiment comprises a sheet of polyurethane adhesive. Asshown, the adhesive sheet 30 is positioned between the film 27 and thepanel side of the substrate 22. Many adhesives or laminations such asPVB, acrylic and/or others can, of course, be used to laminate thesubstrates 22 and 24 together; however, the particular adhesive orlamination materials selected should be capable of exhibitingsubstantially transparent properties upon completion of the lamination.The adhesives may also be tinted or otherwise be provided with IRshielding capabilities, if desired. In accordance with the presentinvention, the layer 30 is positioned between the substrates 22 and 24as shown and then placed in an autoclave under appropriate heat andpressure conditions for approximately three to four hours to laminatethe layers together.

[0049] A further embodiment of the filter in accordance with the presentinvention is shown in FIG. 6. FIG. 6 is similar to the embodiment ofFIG. 3 except that it illustrates a modified film 27′. The film 27′ ofFIG. 6 differs from the film 27 of FIG. 3 in two respects: First, thefilm 27′ includes additional protective or sacrificial layers 53 a, 53 band 53 c adjacent to the layers 52, 56 and 60, respectively, and second,an additional layer 57 is applied over the outer dielectric layer 61 sothat when the substrates are laminated together, the layer 57 ispositioned between the dielectric layer 61 and the adhesive 30.

[0050] As discussed above with respect to the embodiment of FIG. 3, theprotective or sacrificial layers 52, 56 and 60 are preferably titanium.The reasons, among possible others, are that titanium is easily oxidizedand when oxidized, the resulting titanium oxide is clear. As alsodisclosed above with respect to the embodiment of FIG. 3, the dielectriclayers 50, 54 and 58 and 61 are preferably niobium pentoxide (Nb₂O₅).The reasons, among possible others, are that niobium pentoxide has ahigh sputter rate and lower optical dispersion. Despite the distinctadvantages of using titanium and niobium pentoxide as the sacrificiallayer and the dielectric layers, respectively, certain disadvantages orlimitations exist when they are used adjacent to one another or when theconductive material is highly reactive and multiple layers arenecessary. These disadvantages are believed to arise from two primaryfactors. First, the relatively high plasma energy and depositiontemperature of niobium pentoxide adversely affects the protectiveability of the titanium. Thus, when both niobium pentoxide and titaniumare used as in the preferred embodiment, it is necessary to increase thethickness of the sacrificial titanium layers in order to fully protectthe underlying conductive layers (51, 55 or 59) from being oxidized orotherwise damaged during application of the niobium pentoxide. Second,the oxidation of titanium metal is an exothermic reaction. Because moreprotective titanium is needed when it is oxidized in the presence ofniobium pentoxide, the level of heat caused by the exothermic reactionincreases significantly. Because excess heat causes silver toagglomerate, excessive oxidation of titanium can result in damage to theunderlying silver conductive layer.

[0051] To prevent, or at least minimize, the disadvantages associatedwith adjacent layers of titanium and niobium pentoxide as describedabove, and to thereby facilitate the use of both titanium and niobium inthe filter of the present invention, a thin layer of a furtherprotective material 53 a, 53 b and 53 c is applied to the titaniumlayers 52, 56 and 60 as shown in the embodiment of FIG. 6. Preferablythese layers 53 a, 53 b, 53 c are tin oxide which is more durable thantitanium and the underlying silver and which exhibits a significantlyreduced difference in plasma energy level and deposition temperaturerelative to niobium pentoxide. Other materials such as ZnO₂ and SiO₂,among others, may also be used provided they are more durable thantitanium and exhibit a reduced plasma energy level and depositiontemperature, compared to niobium pentoxide. In the embodiment of FIG. 6,the layers 52, 56 and 60 are preferably about 0.5 nm to 15 nm thick andmost preferably about 3 nm to 5 nm thick, while the layers 53 a, 53 band 53 c are preferably about 5 nm to 40 nm thick and most preferablyabout 10 nm to 30 nm thick.

[0052] For the same reasons as discussed above, niobium pentoxide is thepreferred dielectric for the layers 50, 54, 58 and 61, including theouter dielectric layer 61. Despite being preferred, however, strength ofadhesion between the niobium pentoxide outer layer 61 and many of theadhesives is less than desired. To overcome these limitations, theembodiment of FIG. 6 provides a thin layer 57 of silicon dioxide (SiO₂)or other adhesive compatible layer on the outer surface of the outerdielectric layer 61 so that when the substrates 22 and 24 are laminatedtogether with an adhesive 30, the layer 57 is positioned between thelayer 61 and the adhesive 30.

[0053] This additional layer 57 improves the adhesive bond between thecoated substrate 24 and the substrate 22 and thus acts as an adhesionpromoter and also limits any possible reaction between the dielectricand the adhesive. Preferably this layer is silicon dioxide or some othersilicon based composition. However, other materials or compositions willwork as well. The layer 57 is preferably about 2 nm to 50 nm thick andmore preferably about 10 nm to 30 nm thick.

[0054] Both the film 27 of FIGS. 2 and 4 and the film 27′ of FIG. 6provide sufficient sheet resistance to reduce EMI emissions toacceptable levels. Preferably, the films 27 and 27′ function to exhibitsheet resistance of less than 5 ohms per square and more preferably lessthan 1.5 ohms, per square. The films 27 and 27′ also are designed toblock IR emissions and thus reduce the same to acceptable levels, tooptically match the adhesive used to laminate the second substrate andto generally provide desired optical performance by reducing reflectionand improving contrast enhancement.

[0055] During assembly of the filter lamination 15, a busbar 32 isapplied to the outer peripheral edge portion of the substrate 24.Preferably this busbar includes a first leg 34 electrically contactingthe film 27 and extending inwardly from the outer peripheral edge of thesubstrate 24, a second leg 36 applied over the anti-reflective coating26 and also extending inwardly from the outer peripheral edge of thesubstrate 24 and a third leg 35 electrically connected with the legs 34and 36 and essentially extending over the entire peripheral edge of thesubstrate 24. If desired, the legs 35 and 36 can be eliminated as shownin FIG. 4.

[0056] In the preferred embodiment, the legs 34 and 36 extend inwardlyfrom the peripheral edge of the substrate 24 for a distance of at least1.0 mm and preferably a distance greater than or about 2.0 mm. Further,the busbar 32 in accordance with the present invention preferablyextends around the entire periphery of the substrate 24 and thus thefilm 27. It is contemplated that the busbar 32 can be applied in avariety of ways. In the preferred embodiment, however, the busbar 32 isa solder based, electrically conductive material applied via ultrasonicsoldering.

[0057] Following application of the busbar 32 to the peripheral edgeportion of the substrate 24, a conductive environmental degradationbarrier member 38 in the form of electromagnetic shielding tape isapplied over the leg portion 35 of the busbar 32. The member 38 isapplied to the outer or panel side of the anti-reflective coating 26along the outer peripheral edge of such coating 26. The member 38extends inwardly a limited distance from the outermost peripheral edgeof the coating 26. This limited distance is greater than 5 nm andpreferably equal to or greater than about 9 nm. If desired, the barriermember 38 can be applied to all three legs 34, 35 and 36 of the buss bar32. The member 38 is preferably applied to and connected with leg 35 ofthe busbar 32 by an electrically conductive adhesive. Accordingly, themember 38 serves the primary function of making an electrical connectionwith the busbar 32 via the electrically conductive adhesive.

[0058] Grounding means is also provided for electrically connecting themember 38, and thus the busbar 32 and the conductive layers 51, 55 and59, to a grounding terminal 21. In one embodiment as shown in FIGS. 1,2, 4 and 5, this means is in the form of a grounding clip 19 having afirst leg 42 engaging the member 38, a second leg 45 with a springcontact member 46 for making electrical contact with the coating 25 ofthe substrate 22, and a third leg 44 joining the legs 42 and 45. Anelectrical lead 20 has one end connected to the connector clip 19 and asecond end connected with the grounding terminal 21. Other means can ofcourse also be provided for making this electrical grounding connection.

[0059]FIG. 4 shows an alternate embodiment for connecting the busbar 32to the film 27 and connecting the member or tape 38 to the busbar 32. Asshown in FIG. 4, the busbar is comprised only of the leg 34, with thelegs 35 and 36 having been eliminated. In this embodiment a leg 41 ofthe tape 38 is provided directly over the busbar leg 34, with the legs40 and 39 of the tape 38 covering the end and a portion of the face,respectively, of the substrate 24. In his embodiment, both the busbarand the tape would be applied to the substrate 24 before lamination tothe substrate 22.

[0060]FIG. 7 illustrates a further embodiment in accordance with thepresent invention. In the embodiment of FIG. 7, the substrate to whichthe EMI/IR film has been applied is bonded or otherwise applied directlyto the front face of a flat panel or other display. This has severaladvantages. First, it eliminates an additional substrate layer and thussurface reflection from such layer. This accordingly improves theoptical performance of the display. Secondly, direct bonding of thecoated substrate to the front face of the display eliminates the needfor any mounting mechanism for a separate filter such as thatillustrated in FIG. 1. Thirdly, applying the coated substrate directlyto the front face of the display results in a lighter and less complexdisplay unit.

[0061] With reference to FIG. 7, the display is illustrated generally bythe reference character 65 and includes an outer frame 66 and a frontface substrate 68. The coated substrate to be applied to the front facesubstrate 68 includes a substrate 69 preferably constructed of glass ortransparent plastic. This substrate 69, in the embodiment of FIG. 7, isconsidered to be the view side substrate with the substrate 68 of thedisplay 65 being considered the panel side substrate. In the embodimentof FIG. 7, the optical shielding film 70 is applied to the panel side ofthe view side substrate 69. This film 70, in the preferred embodiment,comprises the film 27 of FIG. 3 or the film 27′ of FIG. 6 as describedabove. If desired, an AR coating 71 can also be applied to the view sideof the view side substrate 69. The substrate 69, with the film 70 andthe coating 71 (if desired) applied thereon is laminated or otherwisebonded to the front surface of the display substrate 68. To facilitatethis, an adhesive sheet 72 is positioned between the coated substrate 69and the front face substrate 68 to bond the substrates together. Theadhesive sheet 72 can comprise a polyurethane adhesive, PVB, acrylic orany other materials commonly used as adhesives in such an application.

[0062]FIG. 8 illustrates a further embodiment in accordance with thepresent invention. In the embodiment of FIG. 8, the substrate 69 towhich the optical EMI/IR shielding film 70 has been applied is laminatedto a second substrate 73 comprised of a thin plastic film such as PETwith a thickness less than 0.06 inches (60 mils), more preferably lessthan about 0.025 inches (25 mils) and most preferably less than about0.015 inches (15 mils). While the preferred film substrate 73 is PET,other films such as polycarbonates, acrylics and others may also beused. Materials suitable for use as the film substrate 73 shouldpreferably be optically clear so as to not adversely affect lighttransmission. This entire filter structure is then mounted in front of adisplay unit as shown in FIG. 1, or bonded or otherwise applied directlyto the front face of a flat panel or other display.

[0063] With specific reference to FIG. 8, the display is illustratedgenerally by the reference character 65 and includes an outer frame 66and a front face substrate 68. The coated substrate 69 is preferablyconstructed of glass or transparent plastic and, in the embodiment ofFIG. 8, is considered to be the view side substrate. In the embodimentof FIG. 8, the optical shielding film 70 is applied to the panel side ofthe view side substrate 69 via sputtering or the like. The secondsubstrate 73 in the form of a thin plastic film such as PET as describedabove is then laminated or otherwise applied to the substrate 69 withthe optical film 70 positioned therebetween.

[0064] In one embodiment, this filter structure comprised of thesubstrates 69 and 73 with the film 70 positioned therebetween is thenmounted in front of the display 65 and display substrate 68 such as isshown in FIG. 1. In this embodiment, an anti-reflective (AR) coating 71can be applied to the view side of the substrate 69 and an AR coating 74can be applied to the panel side of the substrate 73 as shown in FIG. 8.If an AR coating is to be applied to the film substrate 73 by atechnique such as sputtering, it is preferable to first apply anabrasion resistant coating or hard coat to the substrate 73 tofacilitate adherence of the sputtered AR coating. Such abrasionresistant coatings are known in the art and can include thermally curedsiloxane based coatings and UV cured acrylic based coatings, amongothers.

[0065] In a further embodiment, the filter comprised of the substrates69 and 73 with the film 70 therebetween may be bonded or otherwiseapplied directly to the front face of the display substrate 68. Thisbonding can be accomplished, if desired, with the use of an adhesivesheet 72 positioned between the PET substrate 73 and the front facesubstrate 68 as shown. In this further embodiment, the AR coating 74 maybe eliminated.

[0066] The method aspect of the present invention, including the methodof forming the filter film on a first substrate and subsequentlylaminating the same to a second substrate can be understood as follows.First, a transparent substrate preferably of glass or plastic isprovided. If desired, the non-coated side surface of such substrate canbe provided with an anti-reflective coating by sputtering or otherdeposition technologies. In some cases this ultimately may be the viewside, while in other cases it may ultimately be the panel side.

[0067] Following this, the film 27 (FIG. 3) or the film 27′ (FIG. 6)comprised of the plurality of dielectric and conductive layers isapplied to the side of the substrate opposite to the anti-reflectivecoating. If no anti-reflective coating is applied, the film 27 or 27′can be applied to either surface. Preferably, the film 27 or 27′ and itsindividual layers are applied by sputtering as previously described.Although the preferred embodiment shows the film 27 or 27′ being applieddirectly to the substrate surface, one or more intermediate layers of afurther material may also be applied to the substrate prior toapplication of the film. Next, for the embodiment of FIG. 2, the busbar32 is applied to the entire peripheral edge portion of the film coatedsubstrate 24. Preferably the legs of the busbar are applied in stageswith the leg 34 first applied to the outer edges of the film 27 or 27′and the leg 35 applied to the outer peripheral edge of the substrate 24.In the embodiment of FIG. 4, the busbar is applied only in the form ofthe leg 34 and the tape or member 38 is then applied to the substrate.

[0068] The film coated substrate is then preferably laminated to asecond substrate 22 which may also be provided with an AR coating,either before or after lamination. The lamination is preferablyaccomplished by positioning the adhesive sheet 30 between the side ofthe substrate 22 opposite the AR coating 25 and the side of thesubstrate 24 carrying the film 27 or 27′. The entire lamination lay-upis then placed in an autoclave under appropriately elevated heat andpressure conditions to laminate the lay-up together. In the preferredprocedure, the lamination lay-up is exposed to a temperature ofapproximately 220° F. and a pressure of approximately 40 p.s.i. forabout three hours. Alternatively, the film coated substrate 24 can beapplied to a plastic film such as PET film or directly to the front faceof a display device.

[0069] When the lamination is complete, the conductive member or tape 38is applied to the outer peripheral edge portions of the filter 15 asillustrated in FIG. 2. The grounding clip or other grounding means 19 isthen applied to the member 38 as shown.

[0070] In the embodiment of FIG. 5, the EMI/IR filter is provided by thelayers 28 and 29. Specifically, a conductive EMI shielding materiallayer 28 is applied to the panel or inner side of the substrate 22 toreduce and limit EMI emissions and an infrared absorbing layer 29 islaminated between the substrates 22 and 24 via the adhesive orlamination layers 33 and 31.

[0071] In the embodiment of FIG. 5, the electrically conductive materiallayer 28 is applied to the panel side of the substrate 22 as shown.Although this layer 28 can be constructed of a variety of materials, itmust preferably include an electrically conductive component or layerwhich provides sufficient electrical conductivity, and thus sufficientlylow electrical resistance, while still maintaining acceptable visiblelight transmission. Preferably, the conductive layer 28 exhibits sheetresistance of less than 5 ohms per square and more preferably less than1.5 ohms per square. The layer 28 provides electromagnetic interference(EMD shielding and assists in reducing EMI emissions to levels whichcomply with consumer safety and other regulations and standards. Thelayer 28 also provides an IR shielding function as well to assist inreducing infrared emissions to acceptable levels. Preferably theconductive layer 28 extends over the entire panel side of the substrate22. This layer 28 can, if desired, comprise a single layer of anelectrically conductive material such as silver or indium tin oxide(ITO) and can also comprise additional layers and materials such asother metals and materials which may be conductive as well asdielectrics and materials which may not be conductive. Such additionallayers and materials can be provided to assist in infrared shielding andreduction of reflection as well as to provide contrast enhancement tothe filter. This may be accomplished by introducing color or tint intothe coating.

[0072] The layer 28 in the present invention can be applied to thesubstrate 22 by any known means. Preferably, however, the layer orlayers which form the electrically conductive material layer 28 isapplied by sputtering or reactive sputtering one or more metals such assilver, gold or copper. The thickness of the layer 28 should preferablybe in the range of less than 2500 Å and most preferably in the range of2000-2500 Å.

[0073] The layer 29 comprises an infrared absorbing film which is aseparate, free-standing film and is sandwiched between, and laminatedto, the substrates 22 an 24 by the lamination material 33 and 31. Theinfrared shielding film 29 can comprise any film which functions toprovide near infrared absorbing capability such as dyed polyethyleneterapthalate (PET) or dyed polyurethane. In the preferred embodiment,the film thickness ranges from 5-10 mils and further includes contrastenhancement capability. The film 29 is effective to reduce the infraredtransmission in the 800 nm-1000 nm range to a level preferably less than20%. At these reduced levels, interference with infrared remote controltransmitters either for the panel display in question or other remotecontrol devices is eliminated.

[0074] The lamination materials 33 and 31 in the preferred embodimentcomprise sheets of polyurethane adhesive. As shown, one adhesive sheet33 is positioned between the film 29 and the coating 28, while the otherpolyurethane adhesive sheet 31 is positioned between the film 29 and theview side of the substrate 24. Many adhesives or laminations such asPVB, acrylic and/or others can, of course, be used to laminate the film29 between the coated substrates 22 and 24; however, the particularadhesive or lamination materials selected should be capable ofexhibiting transparent properties upon completion of the lamination. Theadhesives may also be tinted or otherwise be provided with IR absorbingor shielding capabilities. Preferably, the layers 29, 33 and 31 arepositioned between the substrates 22 and 24 as shown and then are placedin an autoclave under appropriate heat and pressure conditions forapproximately four hours to laminate the layers together.

[0075] Alternative methods of applying the layer 29 may also beutilized. For example, a recently introduced technique involvespositioning the coated substrates 22 and 24 in spaced relationship andsealing the edges so as to form a cavity for accommodating an infraredshielding or absorbing material between the spaced substrates. A liquidor flowable material such as an acrylic into which infrared absorbingmaterial is incorporated is then introduced into the space between thesubstrates so that it flows over the entire substrate surfaces. Thismaterial is then allowed to cure via ultraviolet exposure or otherwiseto produce the infrared absorbing layer.

[0076] The method aspect of the present invention relating to theembodiment of FIG. 5, including the method of making the plasma displaypanel filter, can be understood as follows. First, a pair of transparentsubstrates such as glass or plastic are provided. One of thesesubstrates will ultimately form the view side substrate 22 positioned onthe view side of the filter, while the other substrate will ultimatelyform the panel side substrate 24. Both of these substrates 22 and 24 areprovided with anti-reflective coatings 25 and 26, respectively bysputtering.

[0077] Following this, the EMI shielding layer in the form of theelectrically conductive coating 28 is also applied to the panel side ofthe substrate 22. Preferably, this coating is also applied bysputtering. Next, the busbar 32 is applied to the entire peripheral edgeportion of the substrate 22. Preferably the legs of the busbar areapplied in stages with the leg 34 first applied to the outer edges ofthe coating 28 and the leg 35 applied to the outer peripheral edge ofthe substrate 22.

[0078] The infrared film 29 is then laminated between the coatedsubstrates 22 and 24 by positioning one adhesive sheet 33 between thefilm 29 and the conductive coating 28 of the substrate 22 and a secondadhesive lamination sheet 31 between the other side of the film 29 andthe view side of the substrate 24. The entire lamination lay-up is thenplaced in an autoclave under appropriately elevated heat and pressureconditions to laminate the lay-up together. In one procedure, thelamination lay-up is exposed to a temperature of approximately 220° F.and a pressure of approximately 150 p.s.i. for about four hours.

[0079] When the lamination is complete, the conductive member 38,comprised of the legs 39, 40 and 41, is applied to the outer peripheraledge portions of the filter 15 as illustrated in FIG. 5. The groundingclip 19 is then applied to the member 38 as shown.

[0080] With respect to the embodiment of FIG. 7, the optical shieldingfilm 70 is first applied to one side of substrate 69. If desired, an ARcoating 71 can also be applied to the other side of the substrate 69. Ifapplied, the coating 71 is preferably comprised of a plurality ofindividual layers which together provide the substrate 69 withanti-reflective properties. Next, the substrate 69 is bonded to thefront face of the display substrate 68 by an adhesive sheet 72 or someother bonding technique. Finally, electrical and/or groundingconnections are made in a manner similar to that described above withrespect to the other embodiments.

[0081] With respect to the embodiment of FIG. 8, the method involvesapplying an optical shielding film 70 to one side of a first substrate69. If desired, an AR coating 71 can be applied to the other side of thesubstrate 69. Next, a second substrate 73 in the form of a thin plasticfilm such as PET or other optically clear film is laminated to the firstsubstrate 69 with the optical film 70 positioned therebetween. Next, theentire filter structure is mounted in front of a display 65 as shown inFIG. 1, or otherwise directly bonded to the front surface of the displaysubstrate 68 by an adhesive sheet 72 or some other bonding technique. Ifan AR coating 74 is to be applied to the film substrate 73, it ispreferable to first apply an abrasion resistant coating.

[0082] Although the description of the preferred embodiment and methodhave been quite specific, it is contemplated that various modificationsmay be made without deviating from the—spirit of the present invention.For example, although the preferred embodiment has been described withrespect to a plasma display device, certain features have broaderapplications. For example, the additional protective layer for thesilver or other conductive material may have applications for other thandisplay devices. In general, any application where oxidation or otherdeterioration of the conductive layer is a concern, can use this featureof the invention. Accordingly, it is intended that the scope of thepresent invention be dictated by the appended claims rather than by thedescription of the preferred embodiment and method.

What is claimed is:
 1. An optical display comprising: a transparentfirst substrate having first and second sides; and a multi-layer opticalfilm applied to one of said first and second sides, said film comprisingat least one electrically conductive layer, at least one dielectriclayer and a protective layer positioned between said dielectric layerand said electrically conductive layer; and a second substrate comprisedof a thin plastic film with a thickness less than about 0.06 incheslaminated to said first substrate with said optical film positionedtherebetween.
 2. The display of claim 1 wherein said plastic film isPET.
 3. The display of claim 2 wherein said protective layer iscomprised of first and second layers of protective material.
 4. Thedisplay of claim 3 wherein said dielectric is comprised of niobiumpentoxide.
 5. The display of claim 4 wherein said first protective layeris oxidized titanium and said second layer comprises a material having aplasma energy level less than niobium pentoxide.
 6. The optical filterof claim 5 wherein said second layer is tin oxide.
 7. The optical filterof claim 6 wherein said oxidized titanium is adjacent to saidelectrically conductive layer and said tin oxide is adjacent to saiddielectric layer.
 8. The optical filter of claim 7 wherein saidelectrically conductive layer is silver.
 9. The optical filter of claim1 wherein said second substrate has a thickness of less than about 0.025inches.
 10. The optical film of claim 5 wherein said second protectivematerial layer is one or more of tin oxide (SnO₂), zinc oxide (ZnO₂) anda silicon dioxide (SiO₂).
 11. The optical film of claim 10 wherein saidoxidized titanium is adjacent to said electrically conductive layer andsaid second protective material is adjacent to said dielectric layer.12. The optical film of claim 11 wherein said conductive material layeris silver.
 13. The optical film of claim 12 including a plurality ofelectrically conductive layers and a plurality of dielectric layersalternating with said electrically conductive layers.
 14. A method ofmaking an optical filter comprising: providing a transparent substratehaving a first side and a second side; applying a multi-layer opticalfilm to one of said first and second sides of said transparentsubstrate, said film comprising at least one electrically conductivelayer, at least one dielectric layer, and at least one protective layerbetween said electrically conductive layer and said dielectric layer;and laminating a second substrate to said first substrate with saidoptical film positioned therebetween, said second substrate comprised ofa thin plastic film with a thickness less than about 0.06 inches. 15.The method of claim 14 wherein said plastic film is PET.
 16. The methodof claim 15 wherein said protective layer comprises first and secondlayers.
 17. The method of claim 16 wherein the application step includesapplying an electrically conductive layer to said one side of said firsttransparent substrate or to a dielectric layer applied to said firstsubstrate, applying said first layer to said electrically conductivelayer, applying said second layer to said first layer and applying saiddielectric layer to said second layer.
 18. The method of claim 17wherein said dielectric layer is niobium pentoxide, said first layer istitanium and said second layer is a material having a plasma energylevel less than niobium pentoxide.
 19. The method of claim 18 whereinsaid electrically conductive layer is silver and wherein said secondlayer is one or more of tin oxide (SnO₂), zinc oxide (ZnO₂) and silicondioxide (SiO₂).
 20. The method of claim 14 including applying theoptical filter to the front face of a display.